Method of making coated articles and coated articles made thereby

ABSTRACT

An article includes a first substrate, a functional coating deposited over at least a portion of the substrate, and a protective coating deposited over the functional coating. The functional coating and the protective coating define a coating stack. A polymeric material is deposited over at least a portion of the protective coating. The protective coating has a refractive index that is substantially the same as the refractive index of the polymeric material.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of U.S. application Ser. No.10/133,805 filed Apr. 25, 2002, which was a continuation-in-part of U.S.application Ser. No. 10/007,382 filed Oct. 22, 2001, which claimed thebenefits of U.S. Provisional Application Serial No. 60/242,543 filedOct. 24, 2000, all of which applications are herein incorporated byreference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to coated articles, e.g., coatedautomotive transparencies, and to methods of making the coated articles.

2. Description of the Currently Available Technology

It is known to reduce heat build-up in the interior of a vehicle byproviding a laminated windshield having two glass plies with an infrared(IR) or ultraviolet (UV) attenuating solar control coating positionedbetween the plies to protect the solar control coating from mechanicaland/or chemical damage. These conventional windshields are made byshaping and annealing two flat glass “blanks” (one of which has thesolar control coating deposited thereon) to form two shaped, annealedglass plies and then securing the glass plies together with a plasticinterlayer. Because conventional solar control coatings include metallayers that reflect heat, the glass blanks are typically heated andshaped as “doublets”, i.e., the blanks are positioned one on top ofanother during heating and shaping with the functional coatingsandwiched between the glass blanks to prevent uneven heating andcooling, which can affect the final shape of the plies. Examples oflaminated automotive windshields and methods of making the same aredisclosed in U.S. Pat. Nos. 4,820,902; 5,028,759; and 5,653,903.

The heatability of the doublet is generally limited by the ability ofthe functional coating to withstand the heat treatment without adverselydegrading. By “heatability” is meant the maximum temperature and/ormaximum time at a particular temperature to which the doublet can beheated without degradation of the functional coating. Such degradationcan take the form of oxidation of various metal layers in the coating,which can affect the optical properties of the coating, such as solarenergy reflection and/or transmission.

It would also be advantageous to provide a solar control coating onother automotive transparencies, such as sidelights, back lights,sunroofs, moon roofs, etc. However, the processes of making laminatedwindshields are not easily adapted to making other types of laminatedand/or non-laminated automotive transparencies. For example,conventional automotive sidelights are usually made from a single glassblank that is individually heated, shaped, and tempered to a desiredcurvature dictated by the dimensions of the vehicle opening into whichthe sidelight is to be installed. A problem posed in making sidelightsnot encountered when making windshields is the problem of individuallyheating glass blanks having a heat-reflecting solar control coating.

Additionally, if the sidelight is positioned such that the coating is onthe surface of the sidelight facing away from the vehicle (the outersurface), the coating is susceptible to mechanical damage from objectshitting the coating and to chemical damage from acid rain or car washdetergents. If the coating is on the surface of the sidelight facing theinterior of the vehicle (the inner surface), the coating is susceptibleto mechanical damage from being touched by the vehicle occupants or frombeing rolled up and down in the window channel, and to chemical damagefrom contact with conventional glass cleaners. Additionally, if thecoating is a low emissivity coating it can promote a greenhouse effecttrapping heat inside the vehicle.

While it is known to reduce chemical damage or corrosion to a coating byovercoating with a chemically resistant material, these overcoats aretypically applied as thin as possible so as not to adversely affect theoptical characteristics (e.g., color, reflectance, and transmittance) ofthe underlying coating and so as not to significantly increase theemissivity of the underlying coating. Such thin overcoats typically donot meet the durability requirements for shipping, processing, or enduse of conventional coated automotive transparencies, which are easilydamaged and continuously exposed to the environment. Additionally, suchthin overcoats would not alleviate the greenhouse effect problemdiscussed above. Examples of conventional overcoats are disclosed inU.S. Pat. Nos. 4,716,086; 4,786,563; 5,425,861; 5,344,718; 5,376,455;5,584,902; and 5,532,180.

Therefore, it would be advantageous to provide a method of making anarticle, e.g., a laminated or non-laminated automotive transparency,having a functional coating that reduces or eliminates at least some ofthe problems discussed above.

SUMMARY OF THE INVENTION

An article of the invention comprises at least one substrate, afunctional coating formed over at least a portion of the substrate, anda protective coating formed over at least a portion of the functionalcoating. The functional coating and the protective coating define acoating stack. At least one polymeric material can be formed over theprotective coating. The protective coating can have a refractive indexthat is substantially the same as the refractive index of the polymericmaterial. Thus, little or no undesirable optical effects, such asundesirable changes in color, reflectance, and/or transmittance, withrespect to the coated substrate are caused by the presence of theprotective coating. The article can be a laminated article comprisingtwo or more substrates, with the polymeric material being an interlayermaterial securing at least two of the substrates together.

A particular laminated automotive transparency of the inventioncomprises a first glass substrate having a first major surface and afunctional coating formed over at least a portion of the first majorsurface. The functional coating can comprise at least one metaloxide-containing coating film and at least one infrared reflective metalfilm. A protective coating can be formed over at least a portion of thefunctional coating. The protective coating can comprise 0 wt. % to 100wt. % alumina, such as 5 wt. % to 100 wt. %, 35 wt. % to 100 wt. %alumina and/or 0 wt. % to 100 wt. % silica, such as 0 wt. % to 65 wt. %silica and can have a thickness in the range of 50 Å to 5 microns. Thetransparency further can comprise a second glass substrate and apolymeric material, such as but not limited to polyvinyl butyral,located between the protective coating and the second glass substrate.The material for the protective coating and/or the polymeric materialcan be selected such that the refractive indices of the protectivecoating and the polymeric layer are substantially the same, e.g., within±0.2 of each other.

A monolithic article comprises a substrate, a functional coating formedover at least a portion of the substrate, and a protective coatingformed over at least a portion of the functional coating. The functionalcoating and the protective coating define a coating stack. Theprotective coating can have a thickness in the range of 1 micron to 5microns. A polymeric material can be formed over at least a portion ofthe protective coating. The protective coating can have a refractiveindex that is substantially the same as the refractive index of thepolymeric material.

A method of making a laminated article comprises providing a firstsubstrate; forming a functional coating over at least a portion of thefirst substrate; forming a protective coating over at least a portion ofthe functional coating; and forming a polymeric material over at least aportion of the protective coating. The protective coating and/or thepolymeric material are selected such that the protective coating and thepolymeric material have substantially the same refractive indices.

Another method of the invention comprises providing a first substrate,forming a functional coating over at least a portion of the firstsubstrate, forming a protective coating over at least a portion of thefunctional coating, and providing a second substrate. The first andsecond substrates can be positioned to form a doublet with thefunctional coating positioned between the substrates. The protectivecoating can comprise one or more layers, e.g., such as a single layer,comprising 0 wt. % to 100 wt. % alumina and/or 100 wt. % to 0 wt. %silica, such as 5 wt. % to 100 wt. % alumina and 95 wt. % to 0 wt. %silica, such as 50 wt. % to 70 wt. % alumina and 50 wt. % to 30 wt. %silica. Alternatively, the protective coating can comprise two or morelayers, such as a first layer comprising 5 wt. % to 100 wt. % aluminaand 95 wt. % to 0 wt. % silica, such as 50 wt. % to 70 wt. % alumina and50 wt. % to 30 wt. % silica, and a second layer comprising 30 wt. % to100 wt. % silica and 70 wt. % to 0 wt. % alumina, such as 70 wt. % to100 wt. % silica and 0 wt. % to 30 wt. % alumina. The doublet can beheated and/or shaped. The protective coating can act as an oxygenbarrier to improve the heatability of the doublet by preventing orreducing oxidation of metal layers in the underlying functional coating.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side, sectional view (not to scale) of an edge portion of alaminated automotive transparency, e.g., a sidelight, incorporatingfeatures of the invention;

FIG. 2 is a perspective, partially broken view of an apparatus (withportions removed for clarity) for producing glass blanks G (coated oruncoated) in the practice of the invention;

FIG. 3 is a side, sectional view (not to scale) of a portion of amonolithic article incorporating features of the invention;

FIG. 4 is a graph showing Taber abrasion test results for substrateshaving a protective coating of the invention compared to substrateswithout the protective coating;

FIG. 5 is a graph of the average haze for selected substrates of FIG. 4;

FIG. 6 is a graph of emissivity value versus coating thickness forsubstrates having a protective coating of the invention;

FIG. 7 is a graph showing Taber abrasion test results for substrateshaving a protective coating of the invention; and

FIG. 8 is a bar graph showing the effects of heat treatment and coatingthickness on Taber abrasion for coated substrates having a protectivecoating of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As used herein, spatial or directional terms, such as “left”, “right”,“inner”, “outer”, “above”, “below”, “top”, “bottom”, and the like,relate to the invention as it is shown in the drawing figures. However,it is to be understood that the invention may assume various alternativeorientations and, accordingly, such terms are not to be considered aslimiting. Further, as used herein, all numbers expressing dimensions,physical characteristics, processing parameters, quantities ofingredients, reaction conditions, and the like, used in thespecification and claims are to be understood as being modified in allinstances by the term “about”. Accordingly, unless indicated to thecontrary, the numerical values set forth in the following specificationand claims may vary depending upon the desired properties sought to beobtained by the present invention. At the very least, and not as anattempt to limit the application of the doctrine of equivalents to thescope of the claims, each numerical value should at least be construedin light of the number of reported significant digits and by applyingordinary rounding techniques. Moreover, all ranges disclosed herein areto be understood to encompass the beginning and ending range values andany and all subranges subsumed therein. For example, a stated range of“1 to 10” should be considered to include any and all subranges between(and inclusive of) the minimum value of 1 and the maximum value of 10;that is, all subranges beginning with a minimum value of 1 or more andending with a maximum value of 10 or less, e.g., 5.5 to 10. The terms“flat” or “substantially flat” substrate refer to a substrate that issubstantially planar in form; that is, a substrate lying primarily in asingle geometric plane, which substrate, as would be understood by oneskilled in the art, can include slight bends, projections, ordepressions therein. Further, as used herein, the terms “formed over”,“deposited over”, or “provided over” mean formed, deposited, or providedon but not necessarily in contact with the surface. For example, acoating layer “formed over” a substrate does not preclude the presenceof one or more other coating layers or films of the same or differentcomposition located between the formed coating layer and the substrate.All documents referred to herein are to be understood to be incorporatedby reference in their entirety. As used herein, the terms “polymer” or“polymeric” refer to oligomers, homopolymers, copolymers, andterpolymers, e.g., polymers formed from two or more types of monomers orpolymers.

As will be appreciated from the following discussion, the protectivecoating of the invention can be utilized in making both laminated andnon-laminated, e.g., single substrate, articles. For use with laminatedarticles, the protective coating can usually be thinner than fornon-laminated articles. The structural components and a method of makingan exemplary laminated article of the invention will first be describedand then an exemplary monolithic article of the invention will bedescribed. By “monolithic” is meant having a single structural supportor structural member, e.g., having a single substrate. In the followingdiscussion, the exemplary article (whether laminated or monolithic) isdescribed as an automotive sidelight. However, the invention is notlimited to automotive sidelights but may be used with any articles, suchas but not limited to, insulating glass units, residential or commerciallaminated windows (e.g., skylights), or transparencies for land, air,space, above water and underwater vehicles, e.g. windshields,backlights, sun or moon roofs, just to name a few articles.

FIG. 1 illustrates a laminated article in the form of a sidelight 10incorporating features of the invention. The laminated sidelight 10includes a first substrate or ply 12 having an outer major surface 13and an inner major surface 14. By “ply” is meant a substrate that hasbeen bent to a desired shape or curvature and/or heat treated, such asby annealing or tempering. A functional coating 16 can be formed over,e.g., on, at least a portion, preferably all, of the inner major surface14 in any conventional manner, such as but not limited to chemical vapordeposition, magnetron sputter vapor deposition, spray pyrolysis, just toname a few. As will be described in more detail, a protective coating 17of the invention can be formed over, e.g., on, at least a portion,preferably all, of the functional coating 16 and aids not only inincreasing mechanical and chemical durability but also provides improvedheating characteristics for bending and/or shaping the blank on which itis deposited. A polymeric layer 18 can be located between the first ply12 and a second substrate or ply 20 having an inner major surface 22 andan outer major surface 23. In one non-limiting embodiment, the outermajor surface 23 can face the exterior of the vehicle and the outermajor surface 13 can face the interior of the vehicle. A conventionaledge sealant 26 can be applied to the perimeter of the laminatedsidelight 10 during and/or after lamination in any conventional manner.A decorative band 90, e.g., an opaque, translucent or colored band, suchas a ceramic band, can be provided on a surface of at least one of theplies 12 and 20, for example, around the perimeter of one of the inneror outer major surfaces.

In the broad practice of the invention, the substrates used for firstply 12 and second ply 20 can be of any desired material having anydesired characteristics, such as opaque, translucent, or transparent tovisible light. By “transparent” is meant having a transmittance throughthe substrate of greater than 0% up to 100%. By “visible light” or“visible region” is meant electromagnetic energy in the range of 395nanometers (nm) to 800 nm. Alternatively, the substrate can betranslucent or opaque. By “translucent” is meant allowingelectromagnetic energy (e.g., visible light) to pass through thesubstrate but diffusing this energy such that objects on the side of thesubstrate opposite to the viewer are not clearly visible. By “opaque” ismeant having a visible light transmittance of 0%. Examples of suitablesubstrates include, but are not limited to, plastic substrates (such asacrylic polymers, such as polyacrylates; polyalkylmethacrylates, such aspolymethylmethacrylates, polyethylmethacrylates,polypropylmethacrylates, and the like; polyurethanes; polycarbonates;polyalkylterephthalates, such as polyethyleneterephthalate (PET),polypropyleneterephthalates, polybutyleneterephthalates, and the like;polysiloxane containing polymers; or copolymers of any monomers forpreparing these, or any mixtures thereof); metal substrates, such as butnot limited to galvanized steel, stainless steel, and aluminum; ceramicsubstrates; tile substrates; glass substrates; or mixtures orcombinations of any of the above. For example, the substrate can beconventional untinted soda-lime-silica-glass, i.e., “clear glass”, orcan be tinted or otherwise colored glass, borosilicate glass, leadedglass, tempered, untempered, annealed, or heat-strengthened glass. Theglass may be of any type, such as conventional float glass or flatglass, and may be of any composition having any optical properties,e.g., any value of visible radiation transmission, ultraviolet radiationtransmission, infrared radiation transmission, and/or total solar energytransmission. Types of glass suitable for the practice of the inventionare described, for example but not to be considered as limiting, in U.S.Pat. Nos. 4,746,347; 4,792,536; 5,240,886; 5,385,872; and 5,393,593. Theinvention is not limited by the thickness of the substrate. Thesubstrate can generally be thicker for typical architecturalapplications than for typical vehicle applications. In one embodiment,the substrate can be glass having a thickness in the range of 1 mm to 20mm, such as about 1 mm to 10 mm, such as 2 mm to 6 mm, such as 3 mm to 5mm. For forming a laminated automotive sidelight, the first and secondplies 12, 20 can be less than about 3.0 mm thick, such as less thanabout 2.5 mm thick, such as in the thickness range of about 1.0 mm toabout 2.1 mm. As described below, for monolithic articles the substratecan be thicker.

The functional coating 16 can be of any desired type. As used herein,the term “functional coating” refers to a coating that modifies one ormore physical properties of the substrate over which it is deposited,e.g., optical, thermal, chemical or mechanical properties, and is notintended to be entirely removed from the substrate during subsequentprocessing. The functional coating 16 can have one or more functionalcoating layers or films of the same or different composition orfunctionality. As used herein, the term “film” refers to a coatingregion of a desired or selected coating composition. A “layer” cancomprise one or more “films” and a “coating” can comprise one or more“layers”.

For example, the functional coating 16 can be an electrically conductivecoating, such as, for example, an electrically conductive coating usedto make heatable windows as disclosed in U.S. Pat. Nos. 5,653,903 and5,028,759, or a single-film or multi-film coating used as an antenna.Likewise, the functional coating 16 can be a solar control coating. Asused herein, the term “solar control coating” refers to a coatingcomprised of one or more layers or films which affect the solarproperties of the coated article, such as but not limited to the amountof solar radiation, for example, visible, infrared, or ultravioletradiation incident on and/or passing through the coated article,infrared or ultraviolet absorption or reflection, shading coefficient,emissivity, etc. The solar control coating can block, absorb or filterselected portions of the solar spectrum, such as but not limited to theIR, UV, and/or visible spectrums. Examples of solar control coatingsthat can be used in the practice of the invention are found, for examplebut not to be considered as limiting, in U.S. Pat. Nos. 4,898,789;5,821,001; 4,716,086; 4,610,771; 4,902,580; 4,716,086; 4,806,220;4,898,790; 4,834,857; 4,948,677; 5,059,295; and 5,028,759, and also inU.S. patent application Ser. No. 09/058,440.

The functional coating 16 can also be a low emissivity coating thatallows visible wavelength energy, e.g., 395 nm to 800 nm, to betransmitted through the coating but reflects longer-wavelength solarinfrared energy. By “low emissivity” is meant emissivity less than 0.4,such as less than 0.3, such as less than 0.2, such as less than 0.1,e.g., less than or equal to 0.05. Examples of low emissivity coatingsare found, for example, in U.S. Pat. Nos. 4,952,423 and 4,504,109 andBritish reference GB 2,302,102. The functional coating 16 can be asingle layer coating or multiple layer coating and can include one ormore metals, non-metals, semi-metals, semiconductors, and/or alloys,compounds, composites, combinations, or blends thereof. For example, thefunctional coating 16 can be a single layer metal oxide coating, amultiple layer metal oxide coating, a non-metal oxide coating, ametallic nitride or oxynitride coating, or a non-metallic nitride oroxynitride coating, or a multiple layer coating.

Examples of suitable functional coatings for use with the invention arecommercially available from PPG Industries, Inc. of Pittsburgh, Pa.under the SUNGATE® and SOLARBAN® families of coatings. Such functionalcoatings typically include one or more anti-reflective coating filmscomprising dielectric or anti-reflective materials, such as metal oxidesor oxides of metal alloys, which are transparent to visible light. Thefunctional coating can also include one or more infrared reflectivefilms comprising a reflective metal, e.g., a noble metal such as gold,copper or silver, or combinations or alloys thereof, and can furthercomprise a primer film or barrier film, such as titanium, as is known inthe art, located over and/or under the metal reflective layer. Thefunctional coating can have any desired number of infrared reflectivefilms, such as 1 or more silver layers, e.g., 2 or more silver layers,e.g., 3 or more silver layers.

Although not limiting to the invention, the functional coating 16 can bepositioned on one of the inner major surfaces 14, 22 of the laminate tomake the coating 16 less susceptible to environmental and mechanicalwear than if the functional coating 16 were on an outer surface of thelaminate. However the functional coating 16 could also be provided onone or both of the outer major surfaces 13 or 23. As shown in FIG. 1, aportion of the coating 16, e.g., about a 1 mm to 20 mm, such as 2 mm to4 mm wide area around the outer perimeter of the coated region, can beremoved or deleted in any conventional manner, e.g., by grinding priorto lamination or masking during coating, to minimize damage to thefunctional coating 16 at the edge of the laminate by weathering orenvironmental action during use. In addition, deletion could be done forfunctional performance, e.g., for antennas, heated windshields, or toimprove radio-wave transmission, and the deleted portion can be of anysize. For aesthetic purposes, a colored, opaque, or translucent band 90can be provided over any surface of the plies or the coatings, forexample over one or both surfaces of one or both of the plies, e.g.,around the perimeter of the outer major surface 13, to hide the deletedportion. The band 90 can be made of a ceramic material and may be firedonto the outer major surface 13 in any conventional manner.

The protective coating 17 of the invention can be formed over, e.g., on,at least a portion, preferably all, of the outer surface of thefunctional coating 16. The protective coating 17, among other things,can raise the emissivity of the coating stack (e.g., the functionalcoating plus protective coating) to be greater than the emissivity ofthe functional coating 16 alone. By way of example, if the functionalcoating 16 has an emissivity value of 0.2, the addition of theprotective coating 17 can raise the emissivity value of the resultantcoating stack to an emissivity of greater than 0.2. In one embodiment,the protective coating can increase the emissivity of the resultingcoating stack by a factor of two or more over the emissivity of thefunctional coating alone (e.g., if the emissivity of the functionalcoating is 0.05, the addition of the protective layer can increase theemissivity of the resulting coating stack to 0.1 or more), such as by afactor of five or more, e.g., by a factor of ten or more, e.g., by afactor of twenty or more. In another embodiment of the invention, theprotective coating 17 can raise the emissivity of the resulting coatingstack to be substantially the same as the emissivity of the substrate onwhich the coating is deposited, e.g., within 0.2 of the emissivity ofthe substrate. For example, if the substrate is glass having anemissivity of about 0.84, the protective coating 17 can provide thecoating stack with an emissivity in the range of 0.3 to 0.9, such asgreater than 0.3, e.g., greater than 0.5, e.g., greater than 0.6, e.g.,in the range of 0.5 to 0.9. As will be described below, increasing theemissivity of the functional coating 16 by deposition of the protectivecoating 17 improves the heating and cooling characteristics of thecoated ply 12 during processing. The protective coating 17 also protectsthe functional coating 16 from mechanical and chemical attack duringhandling, storage, transport, and processing.

In one embodiment, the protective coating 17 can have an index ofrefraction (i.e., refractive index) that is substantially the same asthat of the ply 12 to which it is laminated. For example, if the ply 12is glass having an index of refraction of 1.5, the protective coating 17can have an index of refraction of less than 2, such as 1.3 to 1.8,e.g., 1.5±0.2.

The protective coating 17 can be of any desired thickness. In oneexemplary laminated article embodiment, the protective coating 17 canhave a thickness in the range of 100 Å to 50,000 Å, such as 500 Å to50,000 Å, e.g., 500 Å to 10,000 Å, such as 100 Å to 2,000 Å. Further,the protective coating 17 can be of non-uniform thickness across thesurface of the functional coating 17. By “non-uniform thickness” ismeant that the thickness of the protective coating 17 can vary over agiven unit area, e.g., the protective coating 17 can have high and lowspots or areas.

The protective coating 17 can be of any desired material or mixture ofmaterials. In one exemplary embodiment, the protective coating 17 caninclude one or more metal oxide materials, such as but not limited to,aluminum oxide, silicon oxide, or mixtures thereof. For example, theprotective coating can be a single coating layer comprising in the rangeof 0 wt. % to 100 wt. % alumina and/or 0 wt. % to 100 wt. % silica, suchas 5 wt. % to 100 wt. % alumina and 95 wt. % to 0 wt. % silica, such as10 wt. % to 90 wt. % alumina and 90 wt. % to 10 wt. % silica, such as 15wt. % to 90 wt. % alumina and 85 wt. % to 10 wt. % silica, such as 50wt. % to 70 wt. % alumina and 50 wt. % to 30 wt. % silica, such as 35wt. % to 100 wt. % alumina and 65 wt. % to 0 wt. % silica, e.g., 70 wt.% to 90 wt. % alumina and 10 wt. % to 30 wt. % silica, e.g., 75 wt. % to85 wt. % alumina and 15 wt. % to 25 wt. % of silica, e.g., 88 wt. %alumina and 12 wt. % silica, e.g., 65 wt. % to 75 wt. % alumina and 25wt. % to 35 wt. % silica, e.g., 70 wt. % alumina and 30 wt. % silica.Other materials, such as aluminum, chromium, hafnium, yttrium, nickel,boron, phosphorous, titanium, zirconium, and/or oxides thereof, can alsobe present.

Alternatively, the protective coating 17 can be a multilayer coatingformed by separately formed layers of metal oxide materials, such as butnot limited to a bilayer formed by one metal oxide containing layer(e.g., a silica and/or alumina containing first layer) formed overanother meal oxide containing layer (e.g., a silica and/or aluminacontaining second layer). The individual layers of the multilayerprotective coating 17 can be of any desired thickness.

In one embodiment, the protective coating 17 can comprise a first layerformed over the functional coating and a second layer formed over thefirst layer. In one non-limiting embodiment, the first layer cancomprise alumina or a mixture or alloy comprising alumina and silica.For example, the first layer can comprise a silica/alumina mixturehaving greater than 5 wt. % alumina, such as greater than 10 wt. %alumina, such as greater than 15 wt. % alumina, such as greater than 30wt. % alumina, such as greater than 40 wt. % alumina, such as 50 wt. %to 70 wt. % alumina, such as in the range of 70 wt. % to 100 wt. %alumina and 30 wt. % to 0 wt. % silica. In one non-limiting embodiment,the first layer can have a thickness in the range of greater than 0 Å to1 micron, such as 50 Å to 100 Å, such as 100 Å to 250 Å, such as 101 Åto 250 Å, such as 100 Å to 150 Å, such as greater than 100 Å to 125 Å.The second layer can comprise silica or a mixture or alloy comprisingsilica and alumina. For example, the second layer can comprise asilica/alumina mixture having greater than 40 wt. % silica, such asgreater than 50 wt. % silica, such as greater than 60 wt. % silica, suchas greater than 70 wt. % silica, such as greater than 80 wt. % silica,such as in the range of 80 wt. % to 90 wt. % silica and 10 wt. % to 20wt. % alumina, e.g., 85 wt. % silica and 15 wt. % alumina. In onenon-limiting embodiment, the second layer can have a thickness in therange of greater than 0 Å to 2 microns, such as 50 Å to 5,000 Å, such as50 Å to 2,000 Å, such as 100 Å to 1,000 Å, such as 300 Å to 500 Å, suchas 350 Å to 400 Å. As described below, the presence of the protectivecoating 17 can improve the heatability of the functionally coatedsubstrate.

The polymeric layer 18 can include any polymeric material. The“polymeric material” can comprise one polymeric component or cancomprise a mixture of different polymeric components, such as but notlimited to one or more plastic materials, such as but not limited to oneor more thermoset or thermoplastic materials. The polymeric layer 18 canadhere the plies together. Useful thermoset components includepolyesters, epoxides, phenolics, and polyurethanes such as reactioninjected molding urethane (RIM) thermoset materials and mixturesthereof. Useful thermoplastic materials include thermoplasticpolyolefins such as polyethylene and polypropylene, polyamides such asnylon, thermoplastic polyurethanes, thermoplastic polyesters, acrylicpolymers, vinyl polymers, polycarbonates,acrylonitrile-butadiene-styrene (ABS) copolymers, EPDM rubber,copolymers and mixtures thereof.

Suitable acrylic polymers include copolymers of one or more of acrylicacid, methacrylic acid and alkyl esters thereof, such as methylmethacrylate, ethyl methacrylate, hydroxyethyl methacrylate, butylmethacrylate, ethyl acrylate, hydroxyethyl acrylate, butyl acrylate and2-ethylhexyl acrylate. Other suitable acrylics and methods for preparingthe same are disclosed in U.S. Pat. No. 5,196,485.

Useful polyesters and alkyds can be prepared in a known manner bycondensation of polyhydric alcohols, such as ethylene glycol, propyleneglycol, butylene glycol, 1,6-hexylene glycol, neopentyl glycol,trimethylolpropane and pentaerythritol, with polycarboxylic acids suchas adipic acid, maleic acid, fumaric acid, phthalic acids, trimelliticacid or drying oil fatty acids. Examples of suitable polyester materialsare disclosed in U.S. Pat. Nos. 5,739,213 and 5,811,198.

Useful polyurethanes include the reaction products of polymeric polyolssuch as polyester polyols or acrylic polyols with a polyisocyanate,including aromatic diisocyanates such as 4,4′-diphenylmethanediisocyanate, aliphatic diisocyanates such as 1,6-hexamethylenediisocyanate, and cycloaliphatic diisocyanates such as isophoronediisocyanate and 4,4′-methylene-bis(cyclohexyl isocyanate). The term“polyurethane” as used herein is intended to include polyurethanes aswell as polyureas, and poly(urethane-ureas).

Suitable epoxy-functional materials are disclosed in U.S. Pat. No.5,820,987.

Useful vinyl resins include polyvinyl acetal, polyvinyl formal, andpolyvinyl butyral.

The polymeric layer 18 can have any desired thickness, e.g., in onenon-limiting embodiment for polyvinyl butyral the thickness can be inthe range of 0.50 mm to about 0.80 mm, such as 0.76 mm. The polymericmaterial can have any desired refractive index. In one embodiment, thepolymeric material has a refractive index in the range of 1.4 to 1.7,such as 1.5 to 1.6.

The protective coating 17 can have an index of refraction that issubstantially the same as the refractive index of the polymeric layer 18material. By “substantially the same” refractive index-is meant that therefractive index of the protective coating material and the polymericlayer material are the same or sufficiently close that little or noundesirable optical effects, such as undesirable changes in color,reflectance, or transmittance are caused by the presence of theprotective coating 17. In effect, the protective coating 17 behavesoptically as if it were a continuation of the polymeric layer material.The presence of the protective coating 17 preferably does not cause theintroduction of an optically undesirable interface between theprotective coating 17 and the polymeric layer 18. In one embodiment, theprotective coating 17 and polymeric layer 18 can have indices ofrefraction that are within ±0.2 of each other, such as within ±0.1, suchas within ±0.05. By providing that the refractive index of theprotective coating material is the same as or substantially the same asthe refractive index of the polymeric layer material, the presence ofthe protective coating 17 does not adversely impact upon the opticalproperties of the laminated article compared to the optical propertiesof the laminated article without the protective coating 17. For example,if the polymeric layer 18 comprises polyvinyl butyral having an index ofrefraction of 1.5, the protective coating 17 can be selected or formedto have an index of refraction of less than 2, such as 1.3 to 1.8, e.g.,1.5±0.2.

An exemplary method of making a laminated sidelight 10 utilizingfeatures of the invention will now be discussed.

A first substrate and a second substrate are provided. The first andsecond substrates can be flat glass blanks having a thickness of about1.0 mm to 6.0 mm, typically about 1.0 mm to about 3.0 mm, such as about1.5 mm to about 2.3 mm. A functional coating 16 can be formed over atleast a portion of a major surface of the first glass substrate, forexample, the major surface 14. The functional coating 16 can be formedin any conventional manner, such as but not limited to, magnetronsputter vapor deposition (MSVD), pyrolytic deposition such as chemicalvapor deposition (CVD), spray pyrolysis, atmospheric pressure CVD(APCVD), low-pressure CVD (LPCVD), plasma-enhanced CVD (PEVCD), plasmaassisted CVD (PACVD), or thermal evaporation by resistive orelectron-beam heating, cathodic arc deposition, plasma spray deposition,wet chemical deposition (e.g., sol-gel, mirror silvering, etc.), or anyother desired manner. For example, the functional coating 16 can beformed over the first substrate after the first substrate is cut to adesired dimension. Alternatively, the functional coating 16 can beformed over a glass sheet before it is processed and/or over a floatglass ribbon supported on a bath of molten metal, e.g., tin, in aconventional float chamber by one or more conventional CVD coaterspositioned in the float chamber. Upon exiting the float chamber, theribbon can be cut to form the coated first substrate.

Alternatively, the functional coating 16 can be formed over the floatglass ribbon after the ribbon exits the float chamber. For example, U.S.Pat. Nos. 4,584,206, 4,900,110, and 5,714,199 disclose methods andapparatus for depositing a metal-containing film on the bottom surfaceof a glass ribbon. Such a known apparatus can be located downstream of amolten tin bath in the float glass process to provide a functionalcoating on the bottom of the glass ribbon, i.e., the side of the ribbonthat was in contact with the molten metal. Still further, the functionalcoating 16 can be formed over the first substrate by MSVD after thesubstrate has been cut to a desired dimension.

A protective coating 17 of the invention can be formed over at least aportion of the functional coating 16. The protective coating 17 providesseveral processing advantages in making the laminated article. Forexample, the protective coating 17 can protect the functional coating 16from mechanical and/or chemical attack during handling, transport,storage, and processing. Additionally, as described below, theprotective coating 17 can facilitate individual heating and cooling ofthe functionally coated blank by increasing the emissivity of theresulting coating stack. While topcoats have been applied ontofunctional coatings in the past to help protect the functional coatingfrom chemical and mechanical attack during processing, these topcoatswere made as thin as possible so as not to impact upon the aesthetic orsolar control properties of the functional coating, such as the coatingemissivity. Conversely, in the present invention, the protective coating17 can be made sufficiently thick so as to raise the emissivity of thecoating stack. Further, by substantially matching the index ofrefraction of the protective coating 17 to that of the polymeric layer18 material (and/or the substrate to which it is laminated), there islittle or no adverse impact by the presence of the protective coating 17upon the aesthetic and/or optical characteristics of the laminatedarticle 10.

If the functional coating 16 is a low emissivity coating having one ormore infrared reflecting metal layers, the addition of the protectivecoating 17 to raise the emissivity of the coating stack reduces thethermal infrared reflecting characteristics of the functional coating16. However, the coating stack remains solar infrared reflective.

The protective coating 17 can be formed in any conventional manner, suchas but not limited to those described above for applying the functionalcoating, e.g., in-bath or out-of-bath CVD, MSVD, or sol-gel, just toname a few. For example, the substrate with the functional coating canbe directed to a conventional MSVD coating apparatus having one or moremetal electrodes, e.g., cathodes, that can be sputtered in anoxygen-containing atmosphere to form a metal oxide protective coating.In one non-limiting embodiment, the MSVD apparatus can include one ormore cathodes of aluminum, silicon, or mixtures or alloys of aluminum orsilicon. The cathodes can be for example, 5 wt. % to 100 wt. % aluminumand 95 wt. % to 0 wt. % silicon, such as 10 wt. % to 100 wt. % aluminumand 90 wt. % to 0 wt. % silicon, such as 35 wt. % to 100 wt. % aluminumand 0 wt. % to 65 wt. % silicon, e.g., 50 wt. % to 80 wt. % aluminum and20 wt. % to 50 wt. % silicon, e.g., 70 wt. % aluminum and 30 wt. %silicon. Additionally, other materials or dopants, such as aluminum,chromium, hafnium, yttrium, nickel, boron, phosphorous, titanium, orzirconium, can also be present to facilitate sputtering of thecathode(s) and/or to affect the refractive index or durability of theresultant coating. As described above, the protective coating 17 can beformed as a single layer comprising one or more metal oxide materials oras a multilayer coating having two or more separate layers, with eachseparate layer comprising one or more metal oxide materials. Theprotective coating 17 can be applied in a sufficient amount or to asufficient thickness to raise the emissivity of the coating stack overthat of just the functional coating alone. In one embodiment, theprotective coating can be applied to a thickness in the range of 100 Åto 50,000 Å and/or to raise the emissivity of the coating stack togreater than or equal to about 0.3, e.g., greater than or equal to 0.4,e.g., greater than or equal to 0.5.

The functional coating 16 and/or protective coating 17 can be applied tothe flat substrate or to the substrate after the substrate has been bentand shaped to a desired contour.

The coated first substrate and uncoated second substrate can be cut toprovide a first, coated ply and a second, uncoated ply, respectively,each having a desired shape and desired dimensions. The coated anduncoated plies can be seamed, washed, bent, and shaped to a desiredcontour to form the first and second plies 12 and 20, respectively, tobe laminated. As can be appreciated by one of ordinary skill in the art,the overall shapes of the coated and uncoated blanks and plies dependupon the particular vehicle into which they will be incorporated, sincethe final shape of a sidelight differs between different automotivemanufacturers.

The coated and uncoated blanks can be shaped using any desired process.For example, the blanks can be shaped using the “RPR” process disclosedin U.S. Pat. No. 5,286,271 or the modified RPR process disclosed in U.S.Pat. application Ser. No. 09/512,852. FIG. 2 shows an additional RPRapparatus 30 suitable for the practice of the invention and includes afurnace 32, e.g., a radiant heat furnace or tunnel Lehr, having afurnace conveyor 34 comprised of a plurality of spaced furnace conveyorrolls 36. Heaters, such as radiant heater coils, can be positioned aboveand/or below the furnace conveyor 34 along the length of the furnace 32and can be controlled to form heating zones of different temperaturealong the length of the furnace 32.

A shaping station 50 can be located adjacent the discharge end of thefurnace 32 and can include a lower mold 51 having a vertically movableflexible ring 52 and a shaping station conveyor 54 having a plurality ofrolls 56. An upper vacuum mold 58 having a removable or reconfigurableshaping surface 60 of a predetermined shape can be located above thelower mold 51. The vacuum mold 58 can be movable via a shuttlearrangement 61.

A transfer station 62 having a plurality of shaped transfer rolls 64 canbe located adjacent a discharge end of the shaping station 50. Thetransfer rolls 64 can have a transverse elevational curvaturecorresponding substantially to the transverse curvature of the shapingsurface 60.

A tempering or cooling station 70 can be located adjacent a dischargeend of the transfer station 62 and can include a plurality of rolls 72to move the blanks through the station 70 for cooling, tempering, and/orheat strengthening. The rolls 72 can have a transverse elevationalcurvature substantially the same as that of the transfer rolls 64.

In the past, heating functionally coated blanks (substrates) presenteddifficulties due to the heat reflectance of the functional coating 16,which caused uneven heating of the coated and uncoated sides of theblank. U.S. patent application Ser. No. 09/512,852 discloses a method ofovercoming this problem by modifying the RPR heating process to supplyheat primarily toward the non-functionally coated surface of the blank.In the present invention, this problem is addressed by deposition of theemissivity increasing protective coating 17, which allows the same orsubstantially the same heating process to be used both for thefunctionally coated and non-functionally coated blanks.

As shown in FIG. 2, the first blank 80 with the coating stack (e.g.,functional coating 16 and protective coating 17) and thenon-functionally coated second blank 82 can be individually heated,shaped, and cooled prior to lamination. By “individually heated” ismeant that the blanks are not stacked one on top of the other duringheating. In one embodiment, the first blank 80 is placed on the furnaceconveyor 34 with the protective coating 17 facing downwardly, i.e., incontact with the furnace conveyor rolls 36, during the heating process.The presence of the higher emissivity protective coating 17 reduces theproblem of heat reflectance by the metal layers of the functionalcoating 16 and promotes more even heating of the coated and uncoatedsides of the first blank 80. This helps prevent curling of the firstblank 80 common in prior heating processes. In one exemplary embodiment,the blanks are heated to a temperature of about 640° C. to 704° C.during a period of about 10 mins to 30 mins.

At the end of the furnace 32, the softened glass blanks, whether coated80 or non-coated 82, are moved from the furnace 32 to the shapingstation 50 and onto the lower mold 51. The lower mold 51 moves upwardly,lifting the glass blank to press the heat-softened glass blank againstthe shaping surface 60 of the upper mold 58 to conform the glass blankto the shape, e.g., curvature, of the shaping surface 60. The uppersurface of the glass blank is in contact with the shaping surface 60 ofthe upper mold 58 and is held in place by vacuum.

The shuttle arrangement 61 is actuated to move the upper vacuum mold 58from the shaping station 50 to the transfer station 62, where the vacuumis discontinued to release the shaped glass blank onto the curvedtransfer rolls 64. The transfer rolls 64 move the shaped glass blankonto the rolls 72 and into the cooling station 70 for tempering or heatstrengthening in any convenient manner. In the cooling station 70, airis directed from above and below the shaped glass blanks to temper orheat strengthen the glass blanks to form the first and second plies 12and 20. The presence of the high emissivity protective coating 17 alsopromotes more even cooling of the coated blank 80 in the cooling station70.

In another embodiment, the coated and uncoated blanks can be heatedand/or shaped as doublets. In one embodiment, the coated and uncoatedblanks can be positioned such that the functional coating 16 with theprotective coating 17 is located between the two blanks. The blanks canthen be heated and/or shaped in any conventional manner. It is believedthat the protective coating 17 acts as an oxygen barrier to reduce orprevent oxygen passing into the functional coating 16 where the oxygencould react with components of the functional coating 16, such as butnot limited to metals (e.g., silver), to degrade the functional coating16. In one conventional method, the doublet can be placed on a supportand heated to sufficient temperature to bend or shape the blanks to adesired final contour. In the absence of the protective coating 17,typical functionally coated blanks cannot withstand a heating cyclehaving heating above about 1100° F. (593° C.) for more than about twominutes (with heating above 900° F. (482° C.) for more than about sixminutes during the heating cycle) without degradation of the functionalcoating 16. Such degradation can take the form of a hazy or yellowishappearance with a decrease in visible light transmission of 10% or more.Metal layers in the functional coating 16, such as silver layers, canreact with oxygen diffusing into the functional coating 16 or withoxygen present in the functional coating 16. However, it is believedthat utilizing the protective coating 17 will permit the functionallycoated blank to withstand a heating cycle with heating to a temperatureof 1100° F. (593° C.) or more for a period of five to fifteen minutes,such as five to ten minutes, such as five to six minutes (with heatingabove 900° F. (482° C.) for ten to twenty minutes, such as ten tofifteen minutes, such as ten to twelve minutes during the heatingcycle), with no significant degradation of the functional coating 16,e.g., with less than 5% loss of visible light transmission, such as lessthan 3% loss, such as less than 2% loss, such as less than 1% loss, suchas no loss of visible light transmission.

To form the laminated article 10 of the invention, the coated. glass ply12 is positioned with the coated inner major surface 14 facing thesubstantially complimentary inner major surface 22 of the non-coated ply20 and separated therefrom by the polymeric layer 18. A portion, e.g. aband of about 2 mm in width, of the coating 16 and/or protective coating17 can be removed from around the perimeter of the first ply 12 beforelamination. The ceramic band 90 can be provided on one or both of theplies 12 or 20, e.g., on the outer surface 13 of the first ply 12, tohide the non-coated peripheral edge region of the laminated sidelightand/or to provide additional shading to passengers inside the vehicle.The first ply 12, polymeric layer 18 and second ply 20 can be laminatedtogether in any convenient manner, for example but not to be consideredas limiting, as disclosed in U.S. Pat. Nos. 3,281,296; 3,769,133; and5,250,146 to form the laminated sidelight 10 of the invention. An edgesealant 26 can be applied to the edge of the sidelight 10, as shown inFIG. 1.

Although the above method of forming the laminated sidelight 10 of theinvention utilizes an RPR apparatus and method, the sidelight 10 of theinstant invention may be formed with other methods, such as horizontalpress bending methods disclosed, for example, in U.S. Pat. Nos.4,661,139; 4,197,108; 4,272,274; 4,265,650; 4,508,556; 4,830,650;3,459,526; 3,476,540; 3,527,589; and 4,579,577.

FIG. 3 illustrates a monolithic article 100, in particular a monolithicautomotive transparency, incorporating features of the invention. Thearticle 100 includes a substrate or ply 102 having a first major surface104 and a second major surface 106. A functional coating 108 can beformed over at least a portion, such as the majority, e.g., all, of thesurface area of the first major surface 104. A protective coating 110 ofthe invention can be formed over at least a portion, such as themajority, e.g., all, of the surface area of the functional coating 108.The functional coating 108 and protective coating 110 can be formed inany desired method, such as those described above. The functionalcoating 108 and protective coating 110 define a coating stack 112. Thecoating stack 112 can include other coating layers or films, such as butnot limited to a conventional color suppression layer or a sodium iondiffusion barrier layer, just to name a few. An optional polymeric layer113, such as comprising one or more polymeric materials such as thosedescribed above, can be deposited over the protective coating 110 in anydesired manner.

The ply 102 can be of any desired material, such as those describedabove for the plies 12, 20 and can be of any desired thickness. In onenon-limiting embodiment for use as a monolithic automotive sidelight,the ply 102 can have a thickness of less than or equal to 20 mm, e.g.,less than about 10 mm, such as about 2 mm to about 8 mm, e.g., about 2.6mm to about 6 mm.

The functional coating 108 can be of any desired type or thickness, suchas those described above for the functional coating 16. In oneembodiment, the functional coating 108 is a solar control coating havinga thickness of about 600 Å to about 2400 Å.

The protective coating 110 can be of any desired material and have anydesired structure, such as those described above for the protectivecoating 17. The protective coating 110 of the invention can be formed inan amount sufficient to increase, e.g., significantly increase, theemissivity of the coating stack 112 over the emissivity of just thefunctional coating 108 alone. For one exemplary monolithic article, theprotective coating 110 can have a thickness of greater than or equal to1 micron, such as in the range of 1 micron to 5 microns. In oneembodiment, the protective coating 110 increases the emissivity of thecoating stack 112 by at least a factor of 2 over the emissivity of thefunctional coating 108 alone (i.e., if the emissivity of the functionalcoating 108 is 0.05, the addition of the protective coating 110increases the emissivity of the resultant coating stack 112 to at least0.1). In another embodiment, the protective coating 110 increases theemissivity by at least a factor of 5, such as by a factor of 10 or more.In a further embodiment, the protective coating 110 increases theemissivity of the coating stack 112 to 0.5 or more, such as greater than0.6, e.g., in the range of about 0.5 to about 0.8.

Increasing the emissivity of the coating stack 112 maintains the solarenergy reflectance of the functional coating 108 (e.g., reflectance ofelectromagnetic energy in the range of 700 nm to 2100 nm) but decreasesthe thermal energy reflecting capability of the functional coating 108(e.g., reflectance of electromagnetic energy in the range of 5000 nm to25,000 nm). Increasing the emissivity of the functional coating 108 byformation of the protective coating 110 also improves the heating andcooling characteristics of the coated substrate during processing, asdescribed above in discussing the laminated article. The protectivecoating 110 also protects the functional coating 108 from mechanical andchemical attack during handling, storage, transport, and processing.

The protective coating 110 can have an index of refraction which is thesame or substantially the same as that of the ply 102 over which it isdeposited. For example, if the ply 102 is glass having an index ofrefraction of 1.5, the protective coating 110 can have an index ofrefraction of less than 2, such as 1.3 to 1.8, e.g., 1.5±0.2.Additionally or alternatively, the protective coating 110 can have arefractive index that is substantially the same as the refractive indexof the polymeric layer 113.

The protective coating 110 can be of any thickness. In one monolithicembodiment, the protective coating 110 can have a thickness of 1 micronor more to reduce or prevent a color variation in the appearance of thearticle 100. The protective coating 110 can have a thickness less than 5microns, such as in the range of 1 to 3 microns. In one embodiment, theprotective coating 110 can be sufficiently thick to pass theconventional ANSI/SAE 26.1-1996 test with less than 2% gloss loss over1000 revolutions in order to be used as an automotive transparency. Theprotective coating 110 need not be of uniform thickness across thesurface of the functional coating 108 but may have high and low spots orareas.

The protective coating 110 can be a single layer comprising one or moremetal oxide materials, such as those described above. Alternatively, theprotective coating 110 can be a multilayer coating having two or morecoating layers, such as described above. Each coating layer can compriseone or more metal oxide materials. For example, in one embodiment, theprotective coating 110 can comprise a first layer comprising aluminumoxide and a second layer comprising silicon oxide. The individualcoating layers can be of any desired thickness, such as described above.

The substrate with the coating stack 112 can be heated and/or shaped inany desired manner, such as that described above for heating the coatedblank of the laminated article.

The optional polymeric layer. 113 can include one or more polymericcomponents, such as those described above for polymeric layer 18. Thepolymeric layer 113 can be of any desired thickness. In one non-limitingembodiment, the polymeric layer 113 can have a thickness greater than100 Å, such as greater than 500 Å, such as greater than 1000 Å, such asgreater than 1 mm, such as greater than 10 mm, such as in the range of100 Å to 10 mm. The polymeric layer 113 can be a permanent layer (i.e.,not intended to be removed) or can be a temporary layer. By “temporarylayer” is meant a layer intended to be removed, such as but not limitedto removal by combustion or washing with a solvent, in a subsequentprocessing step. The polymeric layer 113 can be formed by anyconventional method.

The monolithic article 100 is particularly useful as an automotivetransparency. As used herein, the term “automotive transparency” refersto an automotive sidelight, back light, moon roof, sunroof, and thelike. The “transparency” can have a visible light transmission of anydesired amount, e.g., 0% to 100%. For vision areas, the visible lighttransmission is preferably greater than 70%. For non-vision areas, thevisible light transmission can be less than 70%.

If the ply 102 with only the functional coating 108 were used as anautomotive transparency, such as a sidelight, the low emissivityfunctional coating 108 could reduce solar energy passing into theautomobile but could also promote a greenhouse effect trapping thermalenergy inside the automobile. The protective coating 110 of theinvention overcomes this problem by providing a coating stack 112 havinga low emissivity functional coating 108 (e.g., emissivity of 0.1 orless) on one side of the coating stack 112 and a high emissivityprotective coating 110 (e.g., emissivity of 0.5 or more) on the otherside. The solar reflecting metal layers in the functional coating 108reduce solar energy passing into the interior of the automobile and thehigh emissivity protective coating 110 reduces the greenhouse effect andpermits thermal energy inside the automobile to be removed.Additionally, layer 110 (or layer 17) can be solar absorbing in one ormore of the UV, IR, and/or visible regions of the electromagneticspectrum.

With respect to FIG. 3, the article 100 can be placed in an automobilewith the protective coating 110 facing a first side 114 of theautomobile and the ply 102 facing a second side 116 of the automobile.If the first side 114 faces the exterior of the vehicle, the coatingstack 112 will reflect solar energy due to the reflective layers presentin the functional coating 108. However, due to the high emissivity,e.g., greater than 0.5, of the coating stack 112, at least some of thethermal energy will be absorbed. The higher the emissivity of thecoating stack 112, the more thermal energy will be absorbed. Theprotective coating 110, in addition to providing increased emissivity tothe coating stack 112, also protects the less durable functional coating108 from mechanical and chemical damage. The optional polymeric layer113 can also provide mechanical and/or chemical durability.

Alternatively, if the first side 114 faces the interior of the vehicle,the article 100 still provides solar reflectance due to the metal layersin the functional coating 108. However, the presence of the protectivecoating 110 reduces thermal energy reflectance by absorbing the thermalenergy to prevent the thermal energy from heating the car interior toelevate its temperature and reduces the greenhouse effect. Thermalenergy from the interior of the vehicle is absorbed by the protectivecoating 110 and is not reflected back into the interior of the vehicle.

Although particularly useful for automotive transparencies, the coatingstack of the invention should not be considered as limited to automotiveapplications. For example, the coating stack can be incorporated into aconventional insulating glass (IG) unit, e.g., can be provided on asurface, either inner or outer surface, of one of the glass sheetsforming the IG unit. If on an inner surface in the air space, thecoating stack would not have to be as mechanically and/or chemicallydurable as it would if on an outer surface. Additionally, the coatingstack could be used in a seasonably adjustable window, such as disclosedin U.S. Pat. No. 4,081,934. If on an outer surface of the window, theprotective coating should be sufficiently thick to protect thefunctional coating from mechanical and/or chemical damage. The inventioncould also be used as a monolithic window.

Illustrating the invention are the following examples which, however,are not to be considered as limiting the invention to their details. Allparts and percentages in the following examples, as well as throughoutthe specification are by weight unless otherwise indicated.

EXAMPLES

Several Samples of functional coatings with different protectivecoatings of the invention were prepared and tested for durability,scattered light haze developed after Taber abrasion, and emissivity. Thefunctional coatings were not optimized for mechanical or opticalproperties but were utilized simply to illustrate the relativeproperties, e.g., durability, emissivity, and/or haze, of afunctionally-coated substrate having a protective coating of theinvention. Methods of preparing such functional coatings are described,for example but not to be considered as limiting, in U.S. Pat. Nos.4,898,789 and 6,010,602.

Test samples were produced by overcoating different functional coatingsas described below (on common soda lime clear glass) with aluminum oxideprotective coatings incorporating features of the invention and havingthickness in the range of 300 Å to 1.5 microns. The functional coatingsused in the tests have high solar infrared reflectance andcharacteristic low emissivity and are comprised of multilayerinterference thin films achieved by depositing alternating layers ofzinc stannate and silver by magnetron sputtering vacuum deposition(MSVD). For the samples discussed below, typically two silver layers andthree zinc stannate layers were present in the functional coating. Thintitanium metal primer layers are also used in the functional coatings ontop of the silver layers to protect the silver layers from oxidationduring MSVD deposition of the oxide zinc stannate layers and to surviveheating to bend the glass substrate. The two functional coatings used inthe following examples differ mainly in the outermost thin layer of themultilayer coating, one being metallic Ti and the other being oxideTiO2. Thickness of either the Ti or TiO₂ outer layer is in the range 10Å to 100 Å. Alternative examples which are equally applicable but whichwere not prepared are functional coatings without a Ti or TiO2 outerlayer or different metallic or oxide outer layers. The functionalcoatings used for the examples having the thin Ti outer layer have ablue reflecting color after heating and with the TiO₂ outer layer have agreen reflecting color after heating. Other resulting reflecting colorsof functional coatings after heating which can be protected with aprotective coating of the invention can be achieved by changing thethickness of the individual silver and zinc stannate layers in thefunctional coating.

Thin or thick aluminum oxide protective coatings for the followingexamples were deposited by mid-frequency, bi-polar, pulsed dualmagnetron reactive sputtering of Al in an Airco ILS 1600, speciallymodified to power two of the three targets. Power was provided by anAdvanced Energy(AE) Pinnacle® Dual DC power supply and Astral® switchingaccessory, that converts the DC supply to a bi-polar, pulsed supply.Glass substrates with the functional coating were introduced into theAirco ILS 1600 MSVD coater having an oxygen reactive oxygen/argonatmosphere. Two aluminum cathodes were sputtered for different times toachieve the different thickness aluminum oxide coatings over thefunctional coatings.

Three sample coupons (Samples A–C) were prepared and evaluated asfollows:

-   Sample A—4 inch by 4 inch (10 cm by 10 cm) pieces of 2 mm thick    clear float glass commercially available from PPG Industries, Inc.,    of Pittsburgh, Pa.-   Sample B—4 inch by 4 inch (10 cm by 10 cm) pieces of 2 mm thick    clear glass coupons having an experimental low emissivity functional    coating approximately 1600 Å thick with green reflecting color    produced by MSVD (as described above) and no protective aluminum    oxide protective coating were used as a control sample.-   Sample C—4 inch by 4 inch (10 cm by 10 cm) pieces of 2 mm thick    glass coupons having an experimental functional coating    approximately 1600 Å thick with blue reflecting color produced by    MSVD but further having a 1.53 micron thick aluminum oxide (Al₂O₃)    protective coating of the invention deposited over the functional    coating.

Replicate Samples A–C were then tested in accordance with a standardTaber Abrasion Test (ANSI/SAE 26.1-1996) and the results are shown inFIG. 4. Scratch density (SD) measurements after Taber for a given numberof cycles were determined by microscope measurements of the totalscratch length of all scratches in a square micron area using digitizingand image analysis software. The Sample C (protective coated) couponsshowed a lower scratch density than the Sample B (functionally coated)coupons. The Sample C coupons had about the same durability as theuncoated glass coupons of Sample A. The Taber results were obtained forthe “as deposited” protective coating, meaning the coated glass couponswere not post-heated after MSVD deposition of the protective coating. Itis expected that the scratch density results should improve (i.e., thescratch density for few Taber cycles should decrease) upon heating ofthe coated substrate due to increased density of the heated coatingstack. For example, the coated substrates could be heated from ambientto a maximum temperature in the range of 640° C. to 704° C. and cooledover a time period of about 10 mins to about 30 mins.

FIG. 5 shows the average scattered light haze versus Taber cycles (inaccordance with ANSI/SAE 26.1-1996) for replicate Samples A and C asdescribed above. Sample A is uncoated glass used as a control. Resultsindicate that the haze that develops for Sample C after 1000 cycles isclose to 2%, the minimum acceptable specified by ANSI for automotiveglazing safety. A modest improvement in the durability of the protectivecoating is expected to result in less than 2% haze after 1000 Tabercycles, exceeding the ANSI safety specification for automotive glazing.

FIG. 6 shows the effect of a protective overcoat of the inventiondeposited at different MSVD process vacuum pressures over two differentfunctional coatings. The Samples shown in FIG. 6 are 2 mm thick couponsof clear float glass with the following coatings deposited thereon:

-   Sample D—control sample; nominally 1600 Å thick blue reflecting    functional coating having no protective coating.-   Sample E—control sample; nominally 1600 Å thick green reflecting    functional coating having no protective coating.-   Sample F(HP)—the functional coating of Sample D plus an aluminum    oxide protective coating sputter deposited as described above at an    MSVD process vacuum pressure of 8 microns of oxygen and argon.-   Sample F(LP)—the functional coating of Sample D plus an aluminum    oxide protective coating sputter deposited as described above at an    MSVD process vacuum pressure of 4 microns of oxygen and argon.-   Sample G(HP)—the functional coating of Sample E plus an aluminum    oxide protective coating sputter deposited as described above at an    MSVD process vacuum pressure of 8 microns of oxygen and argon.-   Sample G(LP)—the functional coating of Sample E plus an aluminum    oxide protective coating sputter deposited as described above at an    MSVD process vacuum pressure of 4 microns of oxygen and argon.

As shown in FIG. 6, as the thickness of the protective coatingincreases, the emissivity of coating stack also increases. At aprotective coating thickness of about 1.5 microns, the coating stack hadan emissivity of greater than about 0.5.

FIG. 7 shows the results of scratch density measurements after 10 cyclesTaber abrasion for Samples F(HP), F(LP), G(HP), and G(LP) describedabove. The control functional Samples D and E with no protective coatinghad initial scratch densities on the order of about 45 mm⁻¹ to 50 mm⁻¹.As shown in FIG. 7, the application of a protective coating of theinvention (even on the order of less than about 800 Å) improves thedurability of the resultant coating stack.

FIG. 8 shows the results of scratch density measurements after 10 cyclesTaber abrasion for the following Samples of blue or green reflectingfunctional coatings with aluminum oxide protective coatings 300 Å, 500Å, and 700 Å thick:

-   Sample H—the functional coating of Sample D plus an aluminum oxide    protective coating sputter deposited as described above by MSVD.-   Sample I—the functional coating of Sample E plus an aluminum oxide    protective coating sputter deposited as described above by MSVD.

As shown on the right side of FIG. 8, heating the coating stack of theinvention improves the durability of the coating stack. The coatings onthe right side of FIG. 8 were heated by insertion in a 1300° F. oven for3 mins, and then removed and placed in a 400° F. oven for 5 mins, afterwhich the coated samples were removed and allowed to cool under ambientconditions.

It will be readily appreciated by those skilled in the art thatmodifications may be made to the invention without departing from theconcepts disclosed in the foregoing description. For example, althoughin the preferred embodiment of the laminated article only one plyincludes a functional coating, it is to be understood that the inventioncould also be practiced with both plies having a functional coating orone ply having a functional coating and the other ply having anon-functional coating, e.g., a photocatalytic coating. Moreover, aswill be appreciated by one of ordinary skill in the art, the preferredoperating parameters described above can be adjusted, if required, fordifferent substrate materials and/or thicknesses. Accordingly, theparticular embodiments described in detail herein are illustrative onlyand are not limiting to the scope of the invention, which is to be giventhe full breadth of the appended claims and any and all equivalentsthereof.

1. A laminated article, comprising: a. a first substrate having a firstmajor surface; b. a functional coating formed over at least a portion ofthe first major surface, wherein the functional coating comprises atleast one metal oxide-containing coating film and at least one infraredreflective metal film; c. a protective coating formed over at least aportion of the functional coating, wherein the protective coatingconsists of a layer comprising a mixture of silica and alumina, whereinthe protective coating has a thickness in the range of 300 Å to 5microns, and wherein the functional coating and the protective coatingdefine a coating stack; d. a second substrate; and e. a polymericmaterial located between the protective coating and the secondsubstrate, wherein the protective coating has a refractive index in therange of ±0.2 with respect to the refractive index of the polymericmaterial.
 2. The article as claimed in claim 1, wherein at least one ofthe first and second substrates is selected from glass, plastic, metal,ceramic, and combinations thereof.
 3. The article as claimed in claim 1,wherein the article is an automotive transparency.
 4. The article asclaimed in claim 1, wherein the functional coating has an emissivity inthe range of greater than 0 to 0.1.
 5. The article as claimed in claim1, wherein the protective coating increases the emissivity of thecoating stack to be at least 0.3.
 6. The article as claimed in claim 1,wherein the protective coating has a refractive index within the rangeof ±0.1 with respect to the refractive index of the polymeric material.7. The article as claimed in claim 1, wherein the polymeric materialcomprises at least one polymer selected from vinyl resin , polyurethane,polyester, acrylic, and epoxy polymers.
 8. The article as claimed inclaim 1, wherein the protective coating is of non-uniform thickness. 9.The article as claimed in claim 1, wherein the first and secondsubstrates comprise glass, the functional coating comprises a solarcontrol coating, the polymeric material comprises polyvinyl butyral, andthe protective coating has a refractive index in the range of 1.5±0.1.10. The article as claimed in claim 1, wherein the protective coatingcomprises at least one layer comprising 15 wt. % to 70 wt. % alumina and85 wt. % to 30 wt. % silica.
 11. A laminated article, comprising: a. afirst substrate having a first major surface; b. a functional coatingformed over at least a portion of the first major surface, wherein thefunctional coating comprises at least one metal oxide-containing coatingfilm and at least one infrared reflective metal film; c. a multilayerprotective coating formed over at least a portion of the functionalcoating to form a coating stack, wherein the protective coating is amultilayer coating comprising a first layer formed over the functionalcoating and a second layer formed over the first layer, wherein thefirst and second layers comprise a mixture of alumina and silica and thefirst layer contains at least 50 wt. % alumina and the second layercontains at least 50 wt. % silica, and wherein the protective coatinghas a thickness in the range of 300 Å to 5 microns; d. a secondsubstrate; and e. a polymeric material located between the first andsecond substrates, with the protective coating having a refractive indexsubstantially the same as the refractive index of the polymericmaterial.
 12. The article as claimed in claim 11, wherein the firstlayer comprises at least 70 wt. % alumina and not more than 30 wt. %silica.
 13. The article as claimed in claim 11, wherein the first layerhas a thickness in the range of 50 Å to 1 micron.
 14. The article asclaimed in claim 11, wherein the first layer has a thickness in therange of 100 Å to 250 Å.
 15. The article as claimed in claim 11, whereinthe second layer comprises at least 70 wt. % silica and not more than 30wt. % alumina.
 16. The article as claimed in claim 11, wherein thesecond layer has a thickness in the range of 50 Å to 2,000 Å.
 17. Thearticle as claimed in claim 11, wherein the second layer has a thicknessin the range of 300 Å to 500 Å.
 18. A monolithic article, comprising: a.a substrate; b. a functional coating formed over at least a portion ofthe substrate, wherein the functional coating comprises at least onemetal oxide-containing coating film and at least one infrared reflectivemetal film; c. a protective coating consisting of a layer comprising amixture of silica and alumina, formed over at least a portion of thefunctional coating, wherein the functional coating and the protectivecoating define a coating stack, and wherein the protective coating has athickness in the range of 300 Å to 5 microns; and d. a polymericmaterial formed over at least a portion of the protective coating,wherein the protective coating has a refractive index that issubstantially the same as the refractive index of the polymericmaterial.
 19. The article as claimed in claim 18, wherein the article isan automotive transparency.
 20. The article as claimed in claim 18,wherein the functional coating has an emissivity of 0.1 or less.
 21. Thearticle as claimed in claim 18, wherein the protective coating comprisesat least one layer comprising 75 wt. % to 85 wt. % alumina and 1 wt. %to 25 wt. % silica.
 22. The article as claimed in claim 18, wherein theprotective coating has a thickness in the range of 1 micron to 5microns.
 23. The article as claimed in claim 18, wherein the protectivecoating has a refractive index within ±0.2 of the refractive index ofthe interlayer material.
 24. The article as claimed in claim 18, whereinthe polymeric material comprises polyvinyl butyral.
 25. The article asclaimed in claim 18, wherein the protective coating has a non-uniformthickness.
 26. A monolithic article, comprising: a. a substrate; b. afunctional coating formed over at least a portion of the substrate,wherein the functional coating comprises at least one metaloxide-containing coating film and at least one infrared reflective metalfilm; c. a multilayer protective coating comprising a first layer formedover the functional coating and a second layer formed over at least aportion of the first layer, wherein the first and second layers comprisea mixture of alumina and silica and the first layer contains at least 50wt. % alumina and the second layer contains at least 50 wt. % silica,wherein the functional coating and the protective coating define acoating stack, and wherein the protective coating has a thickness in therange of 300 Å to 5 microns; and d. a polymeric material formed over atleast a portion of the protective coating, wherein the protectivecoating has a refractive index that is substantially the same as therefractive index of the polymeric material.
 27. The article as claimedin claim 26, wherein the first layer comprises at least 70 wt. % aluminaand not more than 30 wt. % silica.
 28. The article as claimed in claim27, wherein the first layer has a thickness in the range of 50 Å to 1micron.
 29. The article as claimed in claim 28, wherein the first layerhas a thickness in the range of 100 Å to 250 Å.
 30. The article asclaimed in claim 26, wherein the second layer comprises at least 70 wt.% silica and not more than 30 wt. % alumina.
 31. The article as claimedin claim 30, wherein the second layer has a thickness in the range of 50Å to 2,000 Å.
 32. The article as claimed in claim 31, wherein the secondlayer has a thickness in the range of 300 Å to 500 Å.